Irinotecan (CPT-11) is a semisynthetic derivative of camptothecin which acts by inhibiting topoisomerase I. It is our hypothesis that orally administered irinotecan HC1 (CPT-11) is a potent and effective antitumor agent. We are undertaking a phase I trial of oral irinotecan HC1 (CPT-11) in patients with advanced solid tumors. The objectives of the trial are: 1) to determine the MTD and the DLT of CPT-11 when administered orally once per day for five consecutive days every three weeks, 2) to define the safety profile of CPT-11 when administered orally on this schedule, 3) to characterize the single- and multiple-dose pharmacokinetics of CPT-11 and its metabolites, SN-38 and SN-38 glucuronide (SN-38G), and 4) to detect any evidence of antitumor activity. The current trial is very early in the accrual stage with a total of six patients enrolled at two different dose levels. Pharmacokinetic sampling is being performed on days one and five of cycle one. The study drug is being supplied by Pharmacia and Upjohn. Plans for future studies are pending at this time.